Untersuchungen zur differenzialdiagnostischen Bedeutung des IgG-Index und Albuminquotienten bei neurologisch erkrankten Hunden

Investigation of IgG index and albumin quotient for the
differential diagnosis of dogs with neurological diseases In the
present study the benefit of IgG index and albumin quotient for the
differential diagnosis in dogs with neurological diseases was
investigated. The question whether the determination of these two
parameters is a convenient extension of the conventional
cerebrospinal fluid (CSF) examination was explored. The IgG index
served as an indicator for intrathecal IgG synthesis, the albumin
quotient as an indicator for disturbances in the blood-brain
barrier. The concentrations of albumin and IgG in CSF and serum of
122 dogs were determined with the help of nephelometry, followed by
the calculation of the albumin quotient and IgG index. The
conventional CSF examination included cell count, cell morphology,
Pandy’s test, and protein content. All 122 dogs could be
categorized into five different groups according to the clinical
and pathological findings: inflammatory diseases (n = 33), tumors
(n = 11), disc prolaps (n = 37), orthopedic diseases (n = 20), and
idiopathic epilepsy (n = 21). In 10% of the examined dogs (12 of
122), pathological findings of the cerebrospinal fluid could only
be exposed with the help of IgG index or albumin quotient, with the
total protein level being normal. This result was equivalent to 14%
of the dogs with normal total protein levels. Among these patients
were dogs with white dog shaker disease, distemper, steroid
responsive meningitis arteritis, and plexus carcinoma. On the other
side, dogs with increased CSF total protein had a 97% chance of
increased IgG index or albumin quotient. 67% of the dogs with
inflammatory diseases showed an increase in IgG index and 70% an
increase in albumin quotient. In 46% of these animals both
parameters were elevated. Maximum changes were observed in dogs
with central European tick-borne encephalitis. Dogs with white dog
shaker disease were the only ones to exhibit an exclusive increase
in the IgG index. 36% of the patients with tumors showed an
increase in IgG index and 64% an increase in albumin quotient. In
18% of the animals both parameters were elevated. The highest level
of all IgG indices was obtained in a patient with an ependymoma.
Patients with disc prolapse showed in 8% of the cases a mild
increase in IgG index and in 14% a mild increase in albumin
quotient, but never a combination of both. In dogs with orthopedic
diseases, two (10%) had a slight increase in CSF total protein and
albumin quotient, which could not be explained with the orthopedic
findings and which indicated an additional neurological disease. As
expected, no changes occurred with idiopathic epilepsy. Even when
there were highly significant differences between the single groups
of patients, one group never differed significantly from all of the
others groups in both parameters – neither in absolute levels nor
in the proportion of altered values. In dogs with neurological
symptoms without increased levels of protein, IgG index and albumin
quotient can help to identify pathological findings of the
cerebrospinal fluid. In the future, the determination of IgG index
and albumin quotient will be an useful extension of the routinely
used CSF examination in dogs with neurological diseases.